title: Isolation and characterization of a mutant recombinant Saccharomyces cerevisiae strain with high efficiency xylose utilization.
abstract: A recombinant xylose-utilizing Saccharomyces cerevisiae strain carrying one copy of heterologous XYL1 and XYL2 from Pichia stipitis and endogenous XKS1 under the control of the TDH3 promoter in the chromosomal DNA was constructed from the industrial haploid yeast strain NAM34-4C, which showed thermotolerance and acid tolerance. The recombinant S. cerevisiae strain SCB7 grew in minimal medium containing xylose as the sole carbon source, and its shortest generation time (G(short)) was 5 h. From this strain, four mutants showing rapid growth (G(short) = 2.5 h) in the minimal medium were isolated. The mutants carried four mutations that were classified into three linkage groups. Three mutations were dominant and one mutation was recessive to the wild type allele. The recessive mutation was in the PHO13 gene encoding para-nitrophenyl phosphatase. The other mutant genes were not linked to TAL1 gene encoding transaldolase. When the mutants and their parental strain were used for the batch fermentation in a complex medium at pH 4.0 containing 30 g/L xylose at 35 °C with shaking (60 rpm) and an initial cell density (Absorbance at 660 nm) of 1.0, all mutants showed efficient ethanol production and xylose consumption from the early stage of the fermentation culture. In two mutants, within 24 h, 4.8 g/L ethanol was produced, and the ethanol yield was 47%, which was 1.4 times higher than that achieved with the parental strain. The xylose concentration in the medium containing the mutant decreased linearly at a rate of 1 g/L/h until 24 h.
authors.affiliation: Department of Applied Microbial Technology, Faculty of Biotechnology and Life Science, Sojo University, 4-22-1 Ikeda, Kumamoto 860-0082, Japan.
authors.forename: Masataka
authors.initials: M
authors.lastname: Tomitaka
authors.forename: Hisataka
authors.initials: H
authors.lastname: Taguchi
authors.forename: Kohsai
authors.initials: K
authors.lastname: Fukuda
authors.forename: Takashi
authors.initials: T
authors.lastname: Akamatsu
authors.forename: Kenji
authors.initials: K
authors.lastname: Kida
mesh_terms: D009597:4-Nitrophenylphosphatase / Q000235:genetics / Q000378:metabolism; D056804:Biofuels / Q000382:microbiology*; D043364:Endo-1,4-beta Xylanases / Q000235:genetics / Q000378:metabolism; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation; D005799:Genes, Dominant; D005808:Genes, Recessive; D024581:Glyceraldehyde-3-Phosphate Dehydrogenase (Phosphorylating) / Q000235:genetics; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics* / Q000254:growth & development; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism; D014153:Transaldolase / Q000235:genetics / Q000378:metabolism; D014994:Xylose / Q000378:metabolism*
chemical_list: D056804:Biofuels; D029701:Saccharomyces cerevisiae Proteins; D000431:Ethanol; D014994:Xylose; D024581:Glyceraldehyde-3-Phosphate Dehydrogenase (Phosphorylating); C465226:TDH3 protein, S cerevisiae; D014153:Transaldolase; C587993:TAL1 protein, S cerevisiae; D009597:4-Nitrophenylphosphatase; D043364:Endo-1,4-beta Xylanases; C121995:xyl1 xylanase
keywords: Bioethanol; High efficiency of xylose utilization; Recombinant strain; Saccharomyces cerevisiae; Spontaneous mutant